Fix warnings in mirror implementation's diagnostic listener.

sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart

Index: sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
diff --git a/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart b/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
index fe4e6da855f1e3b705f00079eae712c329914f26..8fbb03efbb64a36535799cff08df439b8478626c 100644
--- a/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
+++ b/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
@@ -177,12 +177,24 @@ class Dart2JsDiagnosticListener implements DiagnosticListener {
   void internalError(String message,
                      {Node node, Token token, HInstruction instruction,
                       Element element}) {
-    cancel('Internal error: $message', node, token, instruction, element);
+    cancel('Internal error: $message', node: node, token: token,
+           instruction: instruction, element: element);
   }
 
   void internalErrorOnElement(Element element, String message) {
     internalError(message, element: element);
   }
+
+  SourceSpan spanFromNode(Node node, [Uri uri]) {
+    // TODO(johnniwinther): implement this.
+    throw 'unimplemented';
+  }
+
+  void reportMessage(SourceSpan span, Diagnostic message,
+                     diagnostics.Diagnostic kind) {
+    // TODO(johnniwinther): implement this.
+    throw 'unimplemented';
+  }
 }
 
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